Method and apparatus for imager quality testing

ABSTRACT

An apparatus and method of detecting a defect in an imager die package. The method comprises the steps of exposing the imager die package to light at a first angle, exposing the imager die package to light at a second angle, outputting electrical signals based on the exposures; and determining the level at which a defect is present based on the output electrical signals. An exemplary embodiment of the apparatus comprises a first light source positioned over an imager die package at a first angle, a second light source over the imager die package at a second angle, said first and second angles being different from each other; and a processor for determining a level of defection in the die package.

This application is a continuation application of application Ser. No.10/839,356, now U.S. Pat. No. 7,122,819, filed May 6, 2004, which ishereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for imager diepackage quality testing.

BACKGROUND OF THE INVENTION

Integrated circuits, including dies, for example, imager dies such ascharge-coupled-devices (CCD) and complementary metal oxide semiconductor(CMOS) dies, have commonly been used in photo-imaging applications.

Imager dies, such as the CMOS imager die, typically contain thousands ofpixels in a pixel array to be used in a single chip. Pixels convertlight into an electrical signal that can then be stored and recalled byan electrical device such as, for example, a processor. The electricalsignals that are stored may be recalled to produce an image on, forexample, a computer screen.

Exemplary CMOS imaging circuits, processing steps thereof, and detaileddescriptions of the functions of various CMOS elements of an imagingcircuit are described, for example, in U.S. Pat. Nos. 6,140,630,6,376,868, 6,310,366, 6,326,652, 6,204,524, and 6,333,205, all of whichare assigned to Micron Technology, Inc. The disclosures of each of theforgoing patents are hereby incorporated by reference in their entirety.

FIG. 1 illustrates a block diagram of an imager die 110 having a CMOSimager device 108 formed therein. The CMOS imager device 108 has a pixelarray 114 that comprises a plurality of pixels arranged in apredetermined number of columns and rows. The pixel cells of each row inpixel array 114 are all turned on at the same time by a row select line(not shown), and the pixel cells of each column are selectively outputby respective column select lines (not shown). A plurality of row andcolumn lines are provided for the entire pixel array 114. The row linesare selectively activated in sequence by a row driver 101 in response toa row address decoder 102. The column select lines are selectivelyactivated in sequence for each row activation by a column driver 103 inresponse to a column address decoder 104. The CMOS imager device 108 isoperated by a control circuit 105, which controls the address decoders102, 104 for selecting the appropriate row and column lines for pixelreadout, and row and column driver circuitry 101, 103 to apply drivingvoltage to the drive transistors of the selected row and column lines.

Output signals typically include a pixel reset signal V_(rst), takenfrom a charge storage node after the pixel is reset, and a pixel imagesignal V_(sig), which is taken from the charge storage node aftercharges generated by an image are transferred to the node. The V_(rst)and V_(sig) signals are read by a sample and hold circuit 106 and aresubtracted by a differential amplifier 107, which produces a differencesignal (V_(rst)-V_(sig)) for each pixel cell that represents the amountof light impinging on the pixels. This difference signal is digitized byan analog-to-digital converter 109. The digitized difference signals arethen fed to an image processor 111 to form and output a digital image.In addition, as depicted in FIG. 1, the imager die 110, and, thus, CMOSimager device 108, may be included on a single semiconductor chip.

Imager dies, e.g., imager die 110, are typically packaged and insertedinto imaging devices such as, for example, a digital camera. FIG. 2illustrates a cross-sectional view of one conventional imager diepackage 100. The illustrated package 100 includes the imager die 110positioned on a substrate 112. As discussed above, the imager die 110has an imager device 108 (FIG. 1) having a pixel array 114 formedtherein. In the package 100, the imager die 110 typically has atransparent element 116 over the pixel array 114. The transparentelement 116 is typically attached to the imager die 110 by an adhesivematerial 118, or any other material that can support the transparentelement 116 over the pixel array 114.

In operation, light radiation enters the transparent element 116 of theimager die package 100. The transparent element 116 filters out IRradiation that can cause color shifts in the pixel array 114. Lightradiation is then adsorbed, and image signals are created by the pixelarray 114, which converts the photons from light radiation to electricalsignals, as discussed above with respect to FIG. 1. Wire bonds 122conduct electrical output signals from the imager die 110 to wiring onthe substrate 112, which, in turn, connects to external circuitry.

In displaying an acquired image, a display structure, for example, acomputer screen, will display a complete image only if the completeimage is captured by the pixel array 114. For example, if the pixelarray 114 were subjected to white light from a light source 130 (FIG.5), the expected display image would be an all white image. If the pixelarray 114 is unable to capture the entire image, however, an incompletedisplay image 300, illustrated in FIG. 3, will be displayed on acomputer screen. The illustrated display image 300 appears to have acompletely white surface with a “hole” or defect 124 created by thefailure to capture the complete image (in this case, a white light) fromthe pixel array 114. For the sake of clarity, only a portion of the fullimage having the defect 124 has been illustrated, and has been magnifiedfor illustrative purposes.

The defect 124 may be a result of two separate and distinct causes. Onepossible reason for the defect 124 is that the pixel array contains oneor more non-functional pixels (i.e., the array is defective). A top-downview of a section 400 of a pixel array having a defective pixel isillustrated in FIG. 4. The illustrated section 400 has a singlenon-functional pixel 126. The non-functional pixel 126 may receivelight, but may not be able to convert the light into an electricalsignal that can be stored and recalled as described above with respectto FIG. 1, resulting in a defect 124 (FIG. 3).

Imager die packages having non-functional pixels 126 will likely besegregated into groups by the manufacturer, depending on the number ofnon-functional pixels each package contains. These groups of packages,can be salvaged and used for various applications, or, if necessary, canbe discarded completely. For example, the imager die package 100(FIG. 1) having the non-functional pixel 126 could be used inapplications that do not require the highest resolution, and wouldlikely not be used in high-end applications such as, for example,professional photography equipment. Alternatively, the imager diepackage 100 could be discarded altogether if it contains a significantnumber of non-functional pixels.

A second reason for the image defect 124 (FIG. 3) may be related toparticulate contamination of the transparent element 116 (FIG. 2). FIG.5, for example, illustrates a particle 128 present on the transparentelement 116. The particle 128 may have resulted from the fabricationprocessing of the imager die 110. During testing or operation of theimager die package 100, the particle 128 prevents light from the lightsource 130 from reaching the corresponding pixel (represented by the“X”) of pixel array 114, resulting in the defect 124 illustrated in FIG.3.

Unlike the imager die having a non-functional pixel 126 (FIG. 4), theimager die 110 of FIG. 5 is fully functional. The output of electricalsignals by the fully functional pixel array will, nevertheless, resultin a display image similar to the display image 300 illustrated in FIG.3. Because the particle 128 causes the fully functional array to producea defective output image, the fully functional pixel array will besegregated into the groups of dysfunctional arrays discussed above thatmay be salvaged and used in low-end applications, or discardedaltogether. Discarding fully functional pixel arrays results in loweryield, and increases the overall costs of production.

Accordingly, there is a need and desire for a method and apparatus fortesting the quality of an imager die package, and determining the levelat which the defect is present.

BRIEF SUMMARY OF THE INVENTION

The invention relates to an apparatus and method of detecting a defectin an imager die package. An exemplary embodiment of the methodcomprises the steps of exposing the imager die package to light at afirst angle, exposing the imager die package to light at a second angle,outputting electrical signals based on the exposures; and determiningthe level at which a defect is present based on the electrical signals.An exemplary embodiment of the apparatus comprises a first light sourcepositioned over an imager die package at a first angle, a second lightsource over the imager die package at a second angle, said first andsecond angles being different from each other; and a means fordetermining a level of defects in the die package.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described features of the invention will be more clearlyunderstood from the following detailed description, which is providedwith reference to the accompanying drawings in which:

FIG. 1 is a block diagram of an imager die;

FIG. 2 illustrates a cross-sectional view of an imager die package;

FIG. 3 illustrates a display image;

FIG. 4 illustrates a top-down view of a section of a defective pixelarray;

FIG. 5 illustrates a related apparatus for testing the quality of animager die package;

FIG. 6 illustrates an apparatus for testing the quality of an imager diepackage in accordance with a first exemplary embodiment of theinvention;

FIGS. 7 and 8 illustrate a first exemplary operation of the FIG. 6apparatus;

FIG. 9 illustrates a display image from the operation of the FIG. 6apparatus in accordance with an exemplary embodiment of the invention;

FIGS. 10 and 11 illustrate a second exemplary operation of the FIG. 6apparatus;

FIG. 12 illustrates a display image from the operation of the FIG. 6apparatus in accordance with an exemplary embodiment of the invention;

FIG. 13 illustrates an apparatus for testing the quality of an imagerdie package in accordance with a second exemplary embodiment of theinvention;

FIG. 14 illustrates an apparatus for testing the quality of an imagerdie package in accordance with a third exemplary embodiment of theinvention; and

FIG. 15 is a block diagram of a processor-based system constructed inaccordance with an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof and show by way ofillustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized, and thatstructural, logical, and electrical changes may be made withoutdeparting from the spirit and scope of the present invention. Theprogression of processing steps described is exemplary of embodiments ofthe invention; however, the sequence of steps is not limited to that setforth herein and may be changed as is known in the art, with theexception of steps necessarily occurring in a certain order.

Referring now to the drawings, where like reference numbers designatelike elements, FIGS. 6-12 illustrate a first exemplary embodiment of anapparatus 600 designed to test the quality of an imager die package 100and method of operation. The apparatus 600 includes a light source 130suspended from a suspension structure 601 such that the light source 130is rotatable and can move in relation to the imager die package 100.FIG. 6 illustrates the suspension structure 601 as rotatable around anaxis 603. The apparatus is also illustrated as having the light source130 rotatable around a second axis 604. By being rotatable, the lightsource 130 can emit light onto the imager die package 100, positionedunderneath the light source 130, at various angles. The angles aremeasured in relation to a surface 116 a of the transparent element 116.For example, FIG. 6 illustrates the light source 130 as emitting lightonto the imager die package 100 at an angle represented by θ₁. It shouldbe noted that the light source 130 should be positioned at an angle ofincidence such that the light does not simply reflect off the surface116 a of the transparent element 116, resulting in the failure by thepixel array 114 to capture an image.

In its operation, the imager die package 100 is positioned underneaththe light source 130. The pixel array 114 of the imager die package 100is exposed to light from the light source 130 at a first angle. Theresulting image is stored, and the pixel array 114 is exposed to lightfrom the light source 130 at a second angle. A second image is stored,and the first and second images can be displayed on, for example, acomputer screen. The level at which the defect is present can bedetermined based on the display image, as discussed below in moredetail.

FIG. 7 illustrates the FIG. 6 apparatus 600 as it operates on the imagerdie package 100. The pixel array 114 is exposed to light from the lightsource 130 at a first angle θ₁. The light source 130 could be positionedover the imager die package 100 manually or automatically by, forexample, a computer running a program. A particle 128 on the surface 116a of the transparent element 116 obstructs the path of the light emittedfrom the light source 130. The corresponding pixel (represented by the“X”) fails to receive the light emitted from the light source 130, and,therefore, fails to convert the light into electrical signals. The otherpixels of the pixel array 114 receive the light emitted from the lightsource 130, and convert the light into electrical signals that can bestored and later processed to form an image, as discussed above withrespect to FIG. 1.

FIG. 8 illustrates the light source 130 moved to a different position,and rotated to emit light onto the pixel array 114 of the imager diepackage 100 at a second angle θ₂. The second angle θ₂ is different fromthe first angle θ₁ (FIG. 7). As noted, the light source 130 could bemoved either manually or automatically by, for example, a computerrunning a program. The particle 128 obstructs the light emitted from thelight source 130, and the corresponding pixel (represented by the “Y”)fails to receive the light emitted from the light source 130, and,therefore, fails to convert the light into electrical signals. The otherpixels of the pixel array 114, including the pixel X that failed toreceive light in FIG. 7, receive the light emitted from the light source130, and convert the light into electrical signals that can be stored,and later processed to form an image.

The stored electrical signals are processed, as discussed above withrespect to FIG. 1, to form a display image 900 illustrated in FIG. 9,which is a display of pixels receiving light from both exposures. Theillustrated display image 900 shows two separate defects 124 a, 124 bresulting from the obstruction by the particle 128 (FIGS. 7 and 8)during the operation of the apparatus 600 (FIGS. 7 and 8). The twodefects 124 a, 124 b correspond to the pixels X, Y (FIGS. 7 and 8) thatcould not receive or convert the light emitted from the light source130. The two separate images could be compared by an operator, the imageprocessor 111 (FIG. 1), or a processor-based system, and thedetermination can be made as to whether the defect lies in thetransparent element 116 or the pixel array 114. In this case, the twodefects 124 a, 124 b represent a defect at the transparent element 116level as opposed to the pixel level that is detected by the presentinvention as discussed below with respect to FIGS. 10-12.

FIG. 10 illustrates the apparatus 600 as it operates on an imager diepackage 144 having defective pixels. The defective imager die package144 has a pixel array 150 containing a non-functional pixel, representedby X. The pixel array 150 of the imager die package 144 is exposed tolight emitted from the light source 130 at a first angle θ₁. Thenon-functional pixel X cannot convert the light emitted from the lightsource 130 to electrical signals for subsequent reading and processing.The other pixels in the pixel array, however, are operational, andconvert the light into electrical signals. These signals are storedduring operation.

FIG. 11 illustrates the light source 130 at a different position, and,therefore, a second angle θ₂. The pixel array 150 of the imager diepackage 144 is exposed to light emitted from the light source 130 at asecond angle θ₂. During its operation, non-functional pixel X cannotconvert the light emitted from the light source 130 to electricalsignals for subsequent reading and processing. The other pixels in thepixel array, however, are operational, and convert the light intoelectrical signals. These signals are stored during operation.

The signals stored during operation are outputted as a display image1200 illustrated in FIG. 12 which is a display of pixels receiving lightfrom both exposures. The illustrated display image 1200 only has onedefect 230. The reason for only one defect 230 is that regardless of theangle at which the light source 130 emits light, the non-functionalpixel X (FIGS. 10 and 11) will not convert the light into electricalsignals. In FIGS. 7-9, on the other hand, the pixel upon which theshadow from the particle 128 is cast is dependent upon the angle atwhich the light source 130 emits light.

By using at least two different angles at which the pixel arrays 114,150 (FIGS. 7-11) are exposed to the light source 130, a determinationcan be made as to the level at which the defect is present. For example,an operator or program can determine that the package 100 (FIGS. 7 and8) contains a particle 128 (FIGS. 7 and 8) if two separate defects, e.g.defect 124 a, 124 b (FIG. 9), are detected. Similarly, an operator orprogram can determine that the package 144 (FIGS. 10 and 11) contains anon-functional pixel (e.g., non-functional pixel 126 (FIG. 4)), if onlyone defect, e.g., defect 230 (FIG. 12), is detected.

The method of exposing the pixel array 114 to a light source 130 atdifferent angles improves yields and lowers manufacturing costs by notdiscarding dies having fully functional pixel arrays 114 (FIG. 7), whichhave been obstructed by a particle 128 (FIG. 7). These particles 128(FIG. 7) can be removed from the transparent element 116 (FIG. 7).Oftentimes, the particle 128 (FIG. 7) can be removed by blowers thatpush air along the surface 116 a (FIG. 7) of the transparent element 116(FIG. 7). The fully functional pixel array 114 (FIG. 7) will not beaccidentally discarded, thereby increasing yield, and loweringmanufacturing costs.

FIGS. 13 and 14 illustrate an apparatus 700 according to a secondexemplary embodiment of the invention and a second embodiment of amethod of operation. During operation, the illustrated imager diepackage 100 is positioned under the apparatus 700, which contains twoseparate light sources (a first light source 230 and a second lightsource 232). Although the first light source 230 is illustrated as beingat a 90° angle to the surface 116 a of the transparent element 116, itis not intended to be limiting in any way. For example, the first lightsource 230 could be at an angle less than or greater than 90°, dependingon the desired application.

In the illustrated embodiment, the first and second light sources 230,232 are shown as integrated light sources on a structure having twoposts 702. The posts 702 could be included on all four sides of theapparatus 700, and, together with the first light source 230, comprisean enclosed structure, thereby eliminating any contaminant light fromsources other than the first and second light sources 230, 232. Theelimination of contaminant light ensures that the pixel readings are notinfluenced by light other than the light generated within the apparatus700, i.e., light generated by the first and second light sources 230,232.

It should be noted that the FIG. 13 apparatus 700 is not intended to belimiting in any way. For example, in certain applications, such as“bleaching” of the pixel array 114, it is not necessary to eliminateexternal light sources. Bleaching refers to exposing the pixel array 114to white light, thereby displaying a solid white image on a computerscreen. Bleaching can be used with color pixel arrays, but are primarilyused with black and white pixel arrays. Because certain applications donot require the elimination of external light sources, apparatus 700could have different configurations, as described in greater detailbelow.

The FIG. 13 apparatus operates similarly to the FIG. 6 apparatus 600,with the exception that two light sources 230, 232 are provided ratherthan one (e.g., light source 130 (FIG. 6)). The imager die package 100may be positioned beneath the apparatus 700 by a conveyor belt or someother device that can position the imager die package 100 under theapparatus 700 automatically. The pixel array 114 is exposed to lightfrom the two light sources 230, 232 at different angles, and readingsare taken to form a display image, similar to the display images 900,1200 discussed above with respect to FIGS. 7-12.

By having two separate light sources 230, 232, the apparatus 700 can beoperated by exposing the pixel array 114 of the imager die package 100to light from the two light sources 230, 232 by a number of methods:specifically, the two light sources 230, 232 could be turned onsequentially, i.e., one after the other; overlapping, e.g., exposing thepixel array 114 to light from the first light source 230, andsubsequently exposing the pixel array 114 to light from the second lightsource 232, while the pixel array 114 is exposed to light from the firstlight source 230; or simultaneously, i.e., at the same time.

During sequential operation of the apparatus 700, the exposure of thepixel array 114 to light from the second light source 232 could beavoided if it is determined that there are no defects 124 (e.g., FIG. 3)when the pixel array 114 is exposed to light from the first light source230. The fully functional pixel array 114 would not have to be testedfurther. On the other hand, if a defect 124 (e.g., FIG. 3) is detectedafter exposing the pixel array 114 to light from the first light source230, the second light source 232 can emit light, and two separatedisplay images could be generated. The two separate display images couldbe compared by an operator, the image processor 111 (FIG. 1), or aprocessor-based system, and the determination can be made as to thelevel at which the defect lies (i.e., the transparent element 116 or thepixel array 114).

Alternatively, the images captured by the two exposures could besimultaneously displayed as one display image. An operator, the imageprocessor 111 (FIG. 1), or a processor-based system could determine ifthe defects are in the same location or in different locations. Thelevel at which the defect is present (i.e., whether the defect islocated at the transparent element 116, or the pixel array 114) can bedetermined by this comparison.

In a third apparatus and method of embodiment, illustrated in FIG. 14,an apparatus 800 has first and second light sources 330, 332 that aresuspended from adjustable posts 802. The adjustable posts 802 can beraised and lowered depending on the desired application. Additionally,the illustrated first and second light sources 330, 332 are eachrotatable about an axis 804. By being rotatable, the angle at which thelight sources 330, 332 emit light can be varied during testing, similarto the FIG. 6 apparatus 600. The FIG. 14 configuration allows theapparatus 800 to use the light sources 330, 332 at different angles,thereby ensuring that any particles (e.g., particle 128 (FIG. 7)) on thetransparent element 116 are recognized.

It should be noted that the posts 802 could be suspended from asuspension structure, and do not necessarily have to be touching theimager die package 100 being tested. The posts 802 could be a wire, orsome other structure, and are not limited to the FIG. 14 configuration.It should also be noted that the imager die package 100 could be exposedto light sources 330, 332 either sequentially, simultaneously, oroverlapping, as discussed above with respect to FIG. 13.

Although the invention was described as having light sources 130, 230,232, 330, 332 (FIGS. 7-14) positioned above the imager die packages 100,144 (FIGS. 6-14) being tested, it should be noted that the imager diepackages 100, 144 (FIGS. 6-14) tested can be facing downward, i.e.,having the transparent element 116 (e.g., FIG. 6) facing downward, andexposing the imager die packages 100, 144 (FIGS. 6-14) tested from lightsources 130, 230, 232, 330, 332 (FIGS. 7-14) that are positioned belowthe imager die packages 100, 144 (FIGS. 6-14).

Although the various embodiments of the methods of detecting a defecthave been discussed with exposing the pixel arrays, e.g., pixel array114 (FIG. 6) with light at two different angles, it should be recognizedthat the method may include exposing the pixel arrays with light atseveral different angles. For example, pixel array 114 (FIG. 6) could beexposed to light source 130 (FIG. 6) at a third angle. Similarly,apparatus embodiments 600, 700, 800 (FIGS. 7-14) have been illustratedas having one or two light sources. It should be noted that this is notintended to be limiting in any way, and additional light sources may beincluded in apparatus embodiments 600, 700, 800 (FIGS. 7-14). Forexample, the apparatuses 700 (FIG. 13) could have a third light sourceat a third angle.

It should also be noted that the light sources could comprise of anylight bulb or light emitting source, such as a laser or a light emittingdiode. The light emitting diode could be used with a fiber optic cable.

It should also be noted that the light sources 130, 230, 232, 330, 332(FIGS. 7-14) could use white light, monochromatic lights, or light withdifferent wavelengths, depending on the desired application. Forexample, the light sources could have three different light emittingdiodes each; a red, blue, and green light emitting diode for each lightsource. The light sources 130, 230, 232, 330, 332 (FIGS. 7-14) couldtest color pixel arrays three separate times. The first test would testall of the blue pixels in the pixel array by emitting only blue light,the second test would test all of the green pixels in the pixel array byemitting only green light, and the final test would test all of the redpixels in the pixel array by emitting only red light. During operationof the apparatus embodiments 600, 700, 800 (FIGS. 7-14), the lightsources 130, 230, 232, 330, 332 (FIGS. 7-14) having a plurality of lightemitting diodes could be operated sequentially, simultaneously, or in anoverlapping manner, as described above with respect to FIG. 13.

It should also be noted that the stored electrical signals need not beprocessed to output display images 900, 1200 (FIGS. 9 and 12). Forexample, a program can determine whether defects (e.g., defects 124 a,124 b (FIGS. 7 and 8)) are present within the electrical signalsthemselves. Therefore, display images are not necessarily required, buthave been discussed above with respect to FIGS. 7-14 for illustrativepurposes.

FIG. 15 illustrates a processor-based system 1500 that may be used totest the imager die package 100 (e.g., FIG. 6) in conjunction with oneof the exemplary apparatus embodiments 600, 700, 800 (FIGS. 6-14) of theinvention. The processor-based system 1500 could be programmed tooperate the illustrated embodiments 600, 700, 800 (FIGS. 6-14), andcould be used to determine whether any defects are present in a die. Theprocessor-based system includes an imaging device 1508 being tested. Theimaging device 1508 could be the imager die package 100 (e.g., FIG. 6)itself, or a device including the imager die package 100 (e.g., FIG. 6).Without being limiting, the imaging device 1508 may include a computersystem, camera system, scanner, machine vision, vehicle navigation,video phone, surveillance system, auto focus system, star trackersystem, motion detection system, image stabilization system, medicaldevice, and data compression system.

The processor-based system 1500 generally comprises a central processingunit (CPU) 1502, such as a microprocessor, that communicates with aninput/output (I/O) device 1506 over a bus 1504. Imaging device 1508 alsocommunicates with the CPU 1502 over the bus 1504, and may include theimager die 110 discussed above with respect to FIG. 1. Theprocessor-based system 1500 also includes random access memory (RAM)1510, and can include removable memory 1515, such as flash memory, whichalso communicates with CPU 1502 over the bus 1504. Imaging device 1508may be combined with a processor, such as a CPU, digital signalprocessor, or microprocessor, with or without memory storage on a singleintegrated circuit or on a different chip than the processor, asdiscussed above with respect to FIG. 1.

Any of the memory storage devices in the processor-based system 1500could include a program capable of employing the above-describedfeatures, e.g., moving the light sources 130, 230, 232, 330, 332 (FIGS.7-14), comparing sequential display images, and determining the level atwhich a defect is located. The processor for producing an output imagein accordance with the processes described and illustrated withreference to FIGS. 6-14 may be conducted by the imager processor 111(FIG. 1) within imaging device 1508 or by the CPU 1502, or by yetanother processor communicating with system 1500.

The above description and drawings illustrate exemplary embodimentswhich achieve the objects, features, and advantages of the presentinvention. Although certain advantages and exemplary embodiments havebeen described above, those skilled in the art will recognize thatsubstitutions, additions, deletions, modifications, and/or other changesmay be made without departing from the spirit or scope of the invention.Accordingly, the invention is not limited by the foregoing descriptionbut is only limited by the scope of the appended claims.

1. A method of testing an imager, comprising: exposing the imager havingan array of pixels to light radiation at a plurality of differentincident angles relative to the surface of the imager; capturing arespective image with the pixel array when the imager is exposed tolight radiation at each of the incident angles; outputting electricalsignals representing the respective images; and determining the leveland position of a defect in the imager based on a defect patterndetected in the images.
 2. The method of claim 1, wherein the electricalsignals are processed to generate one or more display images.
 3. Themethod of claim 2, wherein at least one of the display images comprisesa combination of source images, each source image being based on theexposure of the imager to light radiation at a different one of theplurality of incident angles.
 4. The method of claim 1, wherein thelight radiation is emitted by at least two light radiation sources. 5.The method of claim 1, wherein the defect pattern represents a defectivepixel.
 6. The method of claim 1, wherein the defect pattern represents aparticle at least partially obstructing light from reaching aphotosensitive portion of the imager.
 7. The method of claim 1, furthercomprising at least one light radiation source selected from the groupconsisting of a light emitting diode, a light bulb, and a laser.
 8. Themethod of claim 7, wherein the at least one light radiation sourcecomprises a light emitting diode used with a fiber optic cable.
 9. Themethod of claim 1, wherein the exposing step comprises exposure to lightradiation emitted from a plurality of light radiation sourcessimultaneously.
 10. The method of claim 1, wherein the exposing stepcomprises exposure to light radiation emitted from a plurality of lightradiation sources consecutively.
 11. An imager testing apparatus,comprising: at least one light radiation source capable of emittinglight radiation at different incident angles relative to a surface of animager to be tested, and a processor adapted to; process electricalsignals generated by the imager in response to the light radiationexposure at each of the incident angles. generate one or more imagesfrom the electrical signals, wherein at least one of the imagescomprises a combination of source images, each source image being basedon the exposure of the imager to a different one of the incident angles,and determine the level and position of a defect in the imager based onthe generated images.
 12. The imager testing apparatus of claim 11,further comprising a positioning device to position the imager to betested in the imager testing apparatus.
 13. The imager testing apparatusof claim 12, wherein the positioning device is a conveyor belt.
 14. Theimager testing apparatus of claim 11, wherein the imager testingapparatus is enclosed such that the imager to be tested is only exposedto light radiation from the at least one light radiation source.
 15. Theimager testing apparatus of claim 11, wherein a photosensitive portionof the imager to be tested is facing downward and the at least one lightradiation source is below the imager.
 16. An imager die testingapparatus, said apparatus comprising: a single light source; a lightsource positioning apparatus capable of positioning the light sourcesuch that the light source is capable of emitting light radiation to asurface of an imager die package at different incident angles; and aprocessor for analyzing electrical signals output from the imager diepackage to determine a level and position of a defect.
 17. The dietesting apparatus of claim 16, wherein said single light source isselected from the group consisting of a light bulb, a light emittingdiode, a laser, a light emitting diode with fiber optic cable, a whitelight, monochromatic light, and light with an application specificwavelength.
 18. The die testing apparatus of claim 16, wherein saidlight positioning apparatus allows for one or more of light sourcerotation, light source angle adjustment, and light source heightadjustment.
 19. The die testing apparatus of claim 16, wherein saidprocessor converts said electrical signals to defect level and defectposition data without forming comparison images.
 20. An imager dietesting apparatus, said apparatus comprising: a first light sourcepositionable over an imager die at a first angle; a second light sourcepositionable over an imager die at a second angle; and a processor foranalyzing electrical signals output from the imager die in response toexposure from said first light source and said second light source todetermine a level and position of a defect.
 21. A method of detecting adefect in an imager die, said method comprising the acts of: exposingthe imager die to light from at least two distinct angles; outputtingelectrical signals from the imager die package based on said exposuresto light; converting said electrical signals to display images; anddetermining the level and position of a defect by comparison of displayimages.
 22. The method of claim 21 wherein said comparison of displayimages is carried out by a processor system.